PROJECT SUMMARY The Institute of Medicine (IOM), (now the National Academy of Medicine) report issued in March 2011 calls for research that better understand the demographic, social and health inequities of lesbian, gay, bisexual and transgender (LGBT) people and to develop interventions that directly address those disparities. Little is known about the social and sexual networks of Black and Latino sexual and gender minority (SGM) youth most at risk for HIV. Social networks have been suggested as being a key source of health causation through social support, influence and access to resources, whereas sexual networks confer risk for STI/HIV through member characteristics and behavior. RDS has been suggested as an effective tool to reach hard to reach populations including young Black and Latino men who have sex with men (YBLMSM) and transgender women (YBLTW) at risk for or living with HIV. Prior work, however, has demonstrated that nearly half of YBMSM networks are comprised of individuals who are natal sex female (of varying gender and sexual identities). This innovative supplement seeks to expand the parent study to better understand the role of gender and sexually diverse females within the social and sexual networks of YBLMSM and YBLTW and how natal sex female social and sexual networks intersect with YBLMSM and YBLTW networks to promote risk or resilience using the following aims: Aim 1: Characterize the natal sex female social and sexual networks of YBLMSM and YBLTW aged 15-24 years who are at risk for or living with HIV in BWP; Aim 2: Examine the efficiency of including networked young natal sex females (of varying gender and sexual identities) to recruit YBLMSM and YBLTW aged 15-24 years at risk for or living with HIV in BWP; and Aim 3: Determine the demographic, social and reproductive factors in natal sex female social and sexual networks associated with substance use and HIV risk, and the role those factors contribute to HIV risk and substance use in YBLMSM and YBLTW aged 15-24 years old living in BWP. This supplement addresses a significant gap to identify key areas of intervention in the social/sexual networks of YBLMSM and YBLTW; to understand the risk and role of female networks in YBLMSM and YBLTW HIV and substance use behavior; and how to leverage those networks for future intervention.